1. Field of the Invention
The present invention relates to a cleaning agent for use in producing semiconductor devices and a process for producing semiconductor devices using the cleaning agent. In the process of forming a via hole (through hole formed in an insulation film or an interlaminar insulation film to interconnect a lower electrically conductive line pattern and an upper electrically conductive line pattern) and an electrically conductive line pattern on a semiconductor substrate by dry etching in the production of semiconductor devices, a polymeric substance deposits and adheres inside and around the via hole and on the side wall of the conductive line pattern. Therefore, more particularly, the present invention relates to a cleaning agent which can effectively remove such a polymeric deposit without changing the prescribed dimensions of the via hole and the conductive line pattern, and a process for producing semiconductor devices in which the polymeric deposit is effectively removed by the cleaning agent thereby providing high quality semiconductor devices.
2. Description of the Related Arts
In recent semiconductor devices such as ultra-large scale integrated circuits (ULSI), a very small and precise dimension as small as 0.5 .mu.m or less is required to form the circuit patterns.
To meet the above strict requirement in the dimension, the use of a dry etching technique is inevitable in the production of semiconductor devices. However, it has been known that the polymeric deposit containing an etching gas component as well as a component of a film being patterned by dry etching and a component of resist is accumulated at the etched portion as the etching process proceeds. When the polymeric deposit is left remaining, in particular, inside and around the via hole, an upper conductive line pattern and a lower conductive line pattern are connected through the via hole with an increased contact resistance or connected defectively to result in a significant deterioration in the reliability of the semiconductor device. Therefore, the polymeric deposit should be removed sufficiently.
It has been known that the polymeric deposit can be removed by cleaning with a cleaning agent containing hydrofluoric acid or a cleaning agent containing hydrofluoric acid and ammonium fluoride. This method is effective when the lower conductive line pattern is made of a material, such as silicon, tungsten, tungsten-titanium alloys and titanium nitride, which is relatively resistant to corrosion by a fluorine compound. However, when made of a material, such as aluminum and an aluminum alloy containing copper, which is relatively less resistant to corrosion by a fluorine compound, the cleaning agent markedly corrodes and dissolves the conductive line pattern. This makes the electrically sufficient connection between the lower conductive line pattern and the upper conductive line pattern through the via hole impossible, and the electric reliability of the semiconductor device is entirely lost.
Moreover, a cleaning agent containing hydrofluoric acid or a cleaning agent containing hydrofluoric acid and ammonium fluoride is likely to cause corrosion of the insulation film having the via hole, thereby making the hole size larger than the intended size. For example, it has been known that a SOG (spin-on-glass) film made of an organic material and/or an inorganic material, which is one of the insulation films recently coming to be widely used as a smoothing film having a low dielectric constant, easily reacts with a fluorine compound to result in corrosion.
It has been proposed that the polymeric deposit can be removed by a resist remover containing an alkanolamine as the main component (Japanese Patent Application Laid-Open No. 64-88548 and Japanese Patent Application Laid-Open No. 6-222573, etc.) or a resist remover containing an alkanolamine as the main component and a reducing agent as an auxiliary agent (Japanese Patent Application Laid-Open No. 4-289866 and Japanese Patent Application Laid-Open No. 6-266119, etc.). However, the removal of the polymeric deposit by these conventional resist removers frequently requires a heating process in which the electrically conductive line and the insulation films are likely corroded by the action of the resist remover and the heat.
Thus, no effective cleaning method has yet been found for removing the polymeric deposit inside and around the via hole when a SOG film and a conductive line made of aluminum or an aluminum alloy containing copper are exposed to the inner surface of the via hole.
When a film made of aluminum or an aluminum alloy containing copper is subjected to dry etching for forming the conductive line pattern, the polymeric substance deposits on the side wall of the conductive line pattern. Similarly to the polymeric deposit inside and around the via hole, the polymeric deposit on the side wall of the conductive line pattern is not easily removed. Moreover, radicals and ions of chlorine entered into the polymeric deposit react with the moisture absorbed from the surrounding atmosphere during the standing after the etching. As a result thereof, acids are formed and corrode the conductive line pattern. This causes significant adverse effects such as breaking of the conductive line and a short-circuit due to the breaking.
To prevent such a corrosion of conductive line pattern, there has been proposed a method of washing away the radicals and ions by a cleaning treatment using ultra-pure water after dry etching. However, the polymeric deposit on the side wall cannot be removed by this method. Also, complete removal of the radicals and ions remaining in the polymeric deposit is very difficult. Therefore, the corrosion of the conductive line pattern cannot be avoided.
Removal of the polymeric substance deposited during etching of a titanium film or a tungsten film is also difficult. A cleaning treatment by a cleaning agent containing hydrofluoric acid or a cleaning agent containing hydrofluoric acid and ammonium fluoride may remove the polymeric deposit. However, tungsten, titanium, tungsten alloys, titanium alloys, titanium-tungsten alloys and titanium nitride are not sufficiently resistant to corrosion by the fluorine compounds although somewhat resistant thereto. Therefore, the separation of the conductive line pattern, for example, may occur due to a partial corrosion of the conductive line pattern to reduce the electric reliability. When the polymeric deposit is left unremoved, adjacent conductive lines come to contact with each other through the polymeric deposit by the pressure from a film being deposited thereon in the subsequent step, thereby likely to cause a short-circuit and other troubles.